Modular Surgical Instrument with Contained Electrical or Mechanical Systems

ABSTRACT

A surgical instrument includes an elongated shaft module and a handle module selectively separable from one another. The elongated shaft module includes an elongated shaft member and a pair of jaw members supported at a distal end of the elongated shaft member, at least one of the jaw members moveable relative to the other jaw member between open and closed positions. The handle module includes a housing including an opening extending longitudinally therethrough. The opening is dimensioned to permit passage of the pair of jaw members in the closed position. The handle module also includes a movable handle movable relative to the housing to move the pair of jaw members between open and closed positions, and a lock to secure the elongated shaft module in place within the housing.

BACKGROUND

1. Technical Field

The present disclosure relates generally to the field of reposable or reusable surgical instruments. In particular, the disclosure relates to instruments having contained operating systems therein, which facilitates refurbishment of the instruments.

2. Background of Related Art

Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaws that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaws may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode surface to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaws. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis. Thereafter, the sealed tissue may be transected by advancing a knife through the jaws. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al.

In use, various tissue-contacting components of an electrosurgical forceps tend to become contaminated or degraded. For example, electrodes may become contaminated as portions of the treated tissue adhere to the tissue-contacting surfaces of the electrodes. Also, a knife blade may become dull and less effective in transecting sealed tissue after repeated use, even in a single surgical procedure. In order to provide clean electrodes and a sharp knife for a particular surgical procedure, a brand new instrument is often used. Once the procedure is complete, the used instrument is discarded.

Instruments that are reposable, or reusable for multiple procedures, reduce the instrumentation costs per procedure. Providing a reusable electrosurgical forceps, however, presents various challenges. For example, the complexity of an electrosurgical forceps tends to result in fairly labor intensive cleaning procedures to prepare the forceps for subsequent use. Improper cleaning may result in dangerous contamination being introduced surgical site. Also, some reusable forceps have removable and replaceable components to provide clean surfaces for each use. Many of these instruments require arduous disassembly and reassembly procedures that require extensive training, and may discourage use of the instrument.

SUMMARY

The present disclosure describes a surgical instrument for treating tissue. The instrument includes an elongated shaft module and a handle module. The elongated shaft module includes an elongated shaft member and a pair of jaw members supported at a distal end of the elongated shaft member. At least one of the jaw members is moveable relative to the other jaw member between open and closed positions. The handle module includes a housing having an opening extending longitudinally therethrough. The opening is dimensioned to permit passage of the pair of jaw members in the closed position. The handle assembly also includes a movable handle that is movable relative to the housing and operatively coupled to the pair of jaw members such that at least one of the jaw members is induced to move relative to the other jaw member between open and closed positions in response to movement of the movable handle with respect to the housing, and a lock movable between a first position wherein the lock engages the elongated shaft module to secure the elongated shaft module in place within the housing, and a second position wherein the lock is disengaged from the elongated shaft module to permit the elongated shaft module to be separated from the handle module.

The elongated shaft module may include a connector at a proximal end thereof for coupling the instrument to an external source of electrosurgical energy. The elongated shaft module may also include a contained electrical system therein, wherein the electrical system includes an electrical pathway extending between the connector and the end effector that is contained in a substantially moisture impervious casing.

The elongated shaft module may include a reciprocating drive rod extending at least partially through the elongated shaft member and operably coupled to the end effector and the movable handle to induce movement of the jaw members between the open and closed positions in response to movement of the movable handle with respect to the housing to reciprocate the drive rod. The elongated shaft module may include a sealing member coupled to the elongated shaft member at a distal end thereof, and the sealing member may be disposed between the elongated shaft member and the reciprocating drive rod to discourage contaminants from entering the elongated shaft member. The sealing member may be constructed of at least one of an o-ring, a wiper seal and a bellows.

The elongated shaft module may also include a flexible seal member disposed between the jaw members and the outer shaft member, and the flexible seal member may be constructed of heat-shrink tubing. The jaw members may be coupled to the reciprocating drive rod such that the jaw members are induced retract into elongated shaft member in response to reciprocation of the drive rod.

According to another aspect of the disclosure, a surgical instrument includes a handle module including at least one handle providing gripping surfaces for holding the instrument by hand, and a drive assembly selectively removable from the handle assembly. The drive assembly includes an elongated shaft member defining a longitudinal axis and an end effector supported at a distal end of the elongated shaft member. The end effector includes a pair of opposed jaw members wherein at least one of the jaw members is movable relative to the elongated shaft member between open and closed positions with respect to the other jaw member. The drive assembly also includes a reciprocating drive member extending at least partially though the elongated shaft member. The reciprocating drive member operably coupled to the end effector to induce movement of the jaw members between the open and closed positions in response to longitudinal reciprocation of the drive member. A motor is operable to move the reciprocating drive member longitudinally through the elongated shaft, and a substantially moisture-impervious housing substantially surrounds the motor and the reciprocating drive member. An actuator is supported on the housing, and is operable to activate the motor.

The motor may comprise a servomotor or a linear motor. The linear motor may include an electrical coil supported on the elongated shaft member and a magnet supported on the reciprocating drive member, wherein the magnet is longitudinally movable in response to a current in the electrical coil.

The drive assembly may include a cable extending from the housing that is connectable to a source of electrosurgical energy. The cable may be in electrical communication with an electrical conduit extending through the elongated shaft member to transmit an electrosurgical current to the end effector. The drive assembly may also include at least one of a post and a slot disposed thereon configured to snap-fit to at least one of a post and a slot disposed on the handle assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure.

FIG. 1 is a perspective view of an endoscopic surgical instrument having a handle assembly and a removable shaft assembly in accordance with an embodiment of the present disclosure;

FIG. 2 is a perspective view of the handle assembly of the FIG. 1 with a portion of a housing removed depicting interior components of the instrument;

FIG. 3 is a perspective view of the instrument of FIG. 1 depicting the removable shaft assembly separated from the handle assembly;

FIG. 4 is a partial, schematic view of an alternate embodiment of an instrument in accordance with the present disclosure including a handle assembly and a removable module having a contained actuation system;

FIG. 5A is a partial, schematic view of an alternate embodiment of an instrument in accordance with the present disclosure including contained actuation system with a distal end seal;

FIG. 5B is a partial, schematic view of an alternate embodiment of a distal end seal in accordance with the present disclosure;

FIG. 6 is a partial, schematic view of an instrument including a contained actuation system with an alternate embodiment of a distal end seal in accordance with the present disclosure;

FIG. 7 is a schematic view of an alternate embodiment of a contained actuation system in accordance with the present disclosure; and

FIG. 8 is a schematic view of an alternate embodiment of an instrument in a sterile filed coupled to an actuation system positioned outside of the sterile field.

DETAILED DESCRIPTION

Referring initially to FIG. 1, an embodiment of an electrosurgical instrument 10 is depicted. The instrument 10 includes a handle assembly 12 for remotely controlling an end effector 14 through an elongated shaft member 16. Although this configuration is typically associated with instruments for use in laparoscopic or endoscopic surgical procedures, various aspects of the present disclosure may be practiced with traditional open instruments, and in connection with endoluminal procedures as well.

The instrument 10 is coupled to a source of electrosurgical energy, e.g., an electrosurgical generator 18. The generator 18 may include devices such as the LIGASURE® Vessel Sealing Generator and the Force Triad® Generator as sold by Covidien. A cable 20 extends between the handle assembly 12 and the generator 18, and includes a connector 22 for coupling the instrument 10 to the external generator 18. In other embodiments (not shown) a battery powered instrument may be provided in which a generator and connector may be internal or integral to the instrument. The connector 22 includes two prong members 22 a and 22 b that are dimensioned to physically and electrically connect the instrument 10 to opposite terminals, e.g., positive or active (+) and negative or return (−) terminals associated with the generator 18. Thus, bipolar energy may be provided through the instrument 10. Alternatively, the instrument 10 may be configured for delivering monopolar energy to the tissue. In a monopolar configuration, the instrument 10 delivers electrosurgical energy from an active terminal, e.g. (+), while a return pad (not shown) is placed generally beneath a patient and provides a return path to the opposite terminal, e.g. (−), of the generator 18.

To control the end effector 14, the handle assembly 12 includes a stationary handle 24 and movable handle 26. The movable handle 26 may be separated and approximated relative to the stationary handle 24 to respectively open and close the end effector 14. A rotation knob 28 is provided on the handle assembly 12 to permit rotation of the elongated shaft member 16 and the end effector 14 about a longitudinal axis X-X defined by the elongated shaft member 16. A trigger 30 is also disposed on the handle assembly 12, and is operable to extend and retract a knife 136 (see, e.g., FIG. 5A) through the end effector 14. A footswitch (not shown) may be provided to initiate and terminate the delivery of electrosurgical energy to the end effector 14.

Referring now to FIG. 2, the handle assembly 12 is operatively coupled to the end effector 14 (FIG. 1) through a reciprocating drive rod 32 and a knife tube 34 that extend through the elongated shaft member 16. First, the drive rod 32 is operably coupled to the movable handle 26 by an inner sleeve 36 and a link 40 such that pivotal movement of the movable handle 26 induces longitudinal motion of the drive rod 32. The drive rod 32 and the inner sleeve 36 engage one another such that longitudinal motion is transferred therebetween. The inner sleeve 36 and the link 40 engage one another through an upper flange 42 of the link 40 such that pivotal movement of the link 40 induces longitudinal motion of the inner sleeve 36, and, conversely, such that longitudinal motion of the inner sleeve 36 induces pivotal motion of the link 40. The link 40 is pivotally coupled to the movable handle 26 such that pivotal motion may be transferred therebetween. In use, a surgeon may pivot the movable handle 26 toward the stationary handle 24 in the direction of arrow 44, which induces the link 40 to pivot such that the upper flange 42 of the link 40 moves proximally. The proximal movement of the upper flange 42, in turn, draws the inner sleeve 36 and the drive rod 32 in a proximal direction. The proximal movement of the drive rod 32 induces a pair of jaw members 140, 142 (FIG. 5A) of the end effector 14 to move from an open configuration (FIG. 5A) to a closed configuration (FIG. 3) as described in greater detail below with reference to FIG. 5A.

Next, the knife tube 34 is operably coupled to the trigger 30 by an outer sleeve 48. The knife tube 34 and the outer sleeve 48 engage one another such that longitudinal motion is transferred therebetween. The outer sleeve 48 and the trigger 30 engage one another through an upper flange 50 of the trigger 30 such that pivotal movement of the trigger 30 induces longitudinal motion of the outer sleeve 48. In use, a surgeon may pivot the trigger 30 toward the stationary handle 24 in the direction of arrow 52, which induces the upper flange 50 of the trigger 30 to move distally. The distal movement of the upper flange 50, in turn, drives the outer sleeve 48 and the knife tube 34 in a distal direction. The knife tube 34 is coupled to a knife 136 (FIG. 5A) such that the distal movement of the of the knife tube 34 advances the knife through the end effector 14 as described in greater detail below with reference to FIG. 5A.

Referring now to FIG. 3, the instrument 10 is selectively separable into two main modules including the handle assembly 12 and an elongated shaft assembly 60. Separation of the two modules 12, 60 permits use of the instrument in a modular fashion. For example, an alternate elongated shaft assembly (not shown) may be substituted for elongated shaft assembly 60 to provide a more appropriate length for a particular surgical operation. Additionally, separation of the two modules 12, 60 may facilitate cleaning and refurbishment of the instrument 10 by providing ready access to interior components of the instrument 10.

The elongated shaft assembly 60 includes a fully contained electrical system. The entire electrically conductive pathway through the instrument 10, from the prong members 22 a, 22 b to the end effector 14, is part of the elongated shaft assembly 60. Thus, no electrical connections need to be established when assembling the handle assembly 12 and the elongated shaft assembly 60 and the entire electrical pathway may be enclosed in a substantially moisture-impervious casing.

The handle assembly 12 includes a longitudinal opening 62 extending through a housing 64 thereof for receiving the elongated shaft assembly 12. The opening 62 is configured such that the end effector 14 may pass therethrough when arranged in the closed configuration. Thus, the elongated shaft assembly 60 may be assembled to the handle assembly by inserting the end effector 14 into the opening 62 on the proximal side of the instrument 10, and advancing the elongated shaft assembly 60 distally. The trigger 30 may be biased to engage the outer sleeve 48 (FIG. 2), and the link 40 (FIG. 2) may be biased to engage the inner sleeve 36 (FIG. 2) upon sufficient advancement of the elongated shaft assembly 60 distally through the opening 62. The handle assembly 12 also includes a lock 66 thereon, which would permit a surgeon to selectively provide a positive lock to maintain the engagement of the elongated shaft assembly 60 with the handle assembly 12. The lock 66 may be movable between a first position wherein the lock 66 engages the elongated shaft assembly 60 to lock the elongated shaft assembly in place, and a second position wherein the lock 66 disengages the elongated shaft assembly to permit the elongated shaft assembly 60 to be separated from the handle assembly 12.

This modular configuration may be convenient for an operator to assemble since the end effector 14 is provided in a fully assembled condition. Many of the relatively small or delicate components of the end effector 14, such as pivot pin 148 (FIG. 5A), drive pin 144 (FIG. 5A) and knife 136 (FIG. 5A), are preassembled to form a substantial modular unit that is convenient to manipulate by hand. This modular configuration also locates the electrically engaging components, e.g., prong members 22 a, 22 b, at a proximal location substantially spaced from a wet surgical site during use. Proximally locating the electrically engaging components may preserve functionality over time, and may facilitate cleaning of a modular system.

Referring now to FIG. 4, an alternate embodiment of a surgical instrument 70 includes two main components including a handle assembly 72 and a drive assembly 74. The handle assembly 72 includes a slot 76 and a post 78 thereon, which permits the handle assembly 72 to snap onto a post 80 and slot 82 disposed on the drive assembly 74. The handle assembly 72 may provide gripping surfaces for surgeon to hold the instrument 70, but the handle assembly 72 may be otherwise inoperable to control the drive assembly 74.

The drive assembly 74 includes a fully contained electrical system as well as a fully contained mechanical system for controlling the instrument 70. The mechanical system of the drive assembly 74 includes a pair of servomotors 86 and 88 for generating physical or mechanical motion in the instrument 70. The motor 86 engages an elongated shaft member 90 and is operable to rotate the elongated shaft member 90 about a longitudinal axis. Motor 88 engages a drive rod 92, and is operable to translate the drive rod 92 longitudinally through the elongated shaft member 90. Thus, the servomotors 86 and 88 are operable to rotate, open and close and end effector (not shown) as described above with reference to FIG. 1. In other embodiments (not shown), an additional motor may be provided to translate a knife through the elongated shaft.

The electrical system of the drive assembly 74 includes an electrical conduit 96 extending through the elongated shaft member 90. The electrical conduit 96 transmits an electrosurgical current through the elongated shaft member 90 to provide an end effector with an electrosurgical cutting (e-cutting) capability. Electrosurgical cutting is described in greater detail in U.S. Pat. No. 7,270,664 to Johnson et al. The electrical system also includes a circuit board 100. The circuit board 100 is electrically coupled to the motors 88, 86 and to the electrical conduit 96 for providing instructions and electrical power thereto. The circuit board is also electrically coupled to a pair of buttons 102, 104, which a surgeon may depress to activate the motors 88, 86 and to the electrical conduit 96. The buttons 102, 104 are in electrical communication with a cable 106, which may connect the instrument 70 to a source of electrosurgical energy.

A housing 110 surrounds the electrical and mechanical systems of the drive assembly 74, and no electrical connections or mechanical connections to transmit physical motion need to be established to assemble the drive assembly 74 to the handle assembly 72. The housing 110 may thus be configured with a minimum of gaps or crevices where contaminants may become lodged during a surgical procedure. The housing 110 may be substantially impervious to moisture to encase the electrical and mechanical systems therein. This facilitates cleaning and sterilization of the instrument 70 before subsequent use.

Referring now to FIG. 5A, an alternate embodiment of a surgical instrument 114 includes a mechanical system having linear motors 116, 118 for generating physical motion in the instrument 114. The first linear motor 116 includes an electrical coil 120 embedded in an outer shaft member 122 of the instrument 114 and a magnet 124 embedded in a drive rod 126. The second linear motor 118 includes an electrical coil 130 embedded in the outer shaft member 122 and a magnet 134 embedded in a knife 136. By initiating an appropriate electrical current through the coils 120, 130, relative longitudinal motion between the outer shaft member 122 and drive rod 126 and the knife 136 may be induced.

By delivering an appropriate electric current to electrical coil 120, the magnet 124 may be induced to move longitudinally, and thus the drive rod 126 may be induced to move longitudinally since the magnet 124 is imbedded in the drive rod 126. Longitudinal motion of the drive rod 126 induces the end effector 14 to move between the open configuration depicted and the closed configuration (FIG. 3). The end effector 14 includes a pair of jaw members 140, 142, which are coupled to the drive rod 126 by a drive pin 144. The drive pin 144 extends through slots, e.g. drive slot 146, defined in the jaw members 140, 142. The drive slot 146 is arranged obliquely with respect to the elongated shaft member 122 such that longitudinal motion of the drive rod 126 and drive pin 144 induces the jaw members 140, 142 pivot about a pivot pin 148. Thus, activating the linear motor 116 induces the end effector 14 to move between the open and closed configurations.

By delivering an appropriate electric current to electrical coil 130, the magnet 134 may be induced to move longitudinally, and thus the knife 136 may be induced to move longitudinally since the magnet 134 is imbedded in the knife 136. Thus, activating the linear motor 118 may induce the knife 136 to move through the end effector 14 to transect tissue clamped between the jaw members 140, 142.

Since the linear motors 116 and 118 may be activated by electrical signals, the mechanical system of instrument 114 does not require inputs of physical movement from a surgeon to operate the end effector 14. Thus, a proximal end (not shown) of the instrument 114 may be readily sealed. The mechanical system may be fully contained by sealing a distal end of the instrument 114 at appropriate locations. The instrument 114 includes a flexible seal member 150 disposed between the jaw members 140, 142 and the outer shaft member 122. The flexible seal may be constructed of heat-shrink tubing or a similar material, and serves to discourage contaminants from entering the outer shaft member 122. An additional seal member 152 is disposed between the outer shaft member 122 and the knife 136. The seal member 152 is constructed as an o-ring, and prevents contaminants from traveling proximally through the outer shaft member 122. The seals 150, 152 are substantially impervious to moisture, and accommodate the motion of the jaw members 140, 142 and the knife 146 with respect to the outer shaft member 122. The seals facilitate cleaning or sterilization of the instrument 114 since the cleaning or a sterilization medium does not need to penetrate deep into the shaft member 122 or access intricately moving components.

FIG. 5B depicts an alternate embodiment of a seal for preventing contaminants from entering the outer shaft member 122. A wiper seal 158 is provided between the outer shaft member 122 and the knife 136. The wiper seal 158 may be constructed of a generally flat flap of an elastomeric or flexible material circumscribing and fixedly coupled to an interior of the outer shaft member 122. The wiper seal 158 may flex to maintain contact with the knife 136 as the knife 136 moves in a longitudinal direction. Additional wiper seals (not shown) or other seals may be provided between the knife 136 and the drive rod 126 or between the outer shaft member 122 and the drive rod 126.

Referring now to FIG. 6, an alternate embodiment of a surgical instrument 164 includes an alternate seal for preventing contaminants from entering the outer shaft member 122. The instrument 164 includes a bellows seal 166 disposed between the outer shaft member 122 and the knife 136. The bellows seal includes folds that permit the bellows seal to expand and contract longitudinally to accommodate the motion of the knife 136 with respect to the outer shaft member 122. In some embodiments (not shown), a bellows seal may be provided between the end effector 14 and outer shaft member 122, or in other locations to discourage ingress of contaminants into the outer shaft member 122.

Referring now to FIG. 7, an alternate embodiment of a surgical instrument 172 includes an alternate end effector 174 for facilitating cleaning and refurbishment of the instrument 172. The end effector 174 includes a drive tube 178 with a pair of jaw members 180, 182 formed at a distal end thereof. The drive tube 178 and jaw members 180, 182 are longitudinally movable with respect to an outer shaft 184. The jaws 180, 182 may be integrally formed with the drive tube 178 and may include flexible proximal ends that allow the jaws 180, 182 to close when retracted into the outer shaft 184. This type of mechanism for closing the jaw members 180, 182 reduces the number and complexity of components in the end effector 174, and may thus promote cleanliness and facilitate assembly of the instrument 172. In other embodiments (not shown), a pair of retractable jaw members may be coupled to one another by a pivot pin, and a compression spring (not shown) may be provided to bias the jaw members to a distal and open configuration.

A cable 190 is coupled to the end effector 174 and drive rod 178 such that the entire electrical system of the instrument 172 may be contained in a single module. Thus, no electrical connections must be established to assemble the instrument 172.

Referring now to FIG. 8, an alternate embodiment of an instrument 200 includes an instrument body 202 and a service module 204. The service module 204 may include components to provide electrical and mechanical power to the instrument body 202. For example, the service module 204 may include an electrosurgical generator and/or pneumatics or hydraulics configured to move parts of the instrument body 202. The instrument body 202 is mechanically and electrically coupled to the service module 204 by a conduit 206 including a separable connector 208. The connector 208 is disposed on the conduit 206 at a sufficient distance from the instrument body 202 to be located outside a surgical field 210 when the instrument 200 is in use.

Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims. 

What is claimed is:
 1. A surgical instrument, comprising: an elongated shaft module including: an elongated shaft member; and an end effector including a pair of jaw members supported at a distal end of the elongated shaft member, at least one of the jaw members moveable relative to the other jaw member between open and closed positions; and a handle module including: a housing including an opening extending longitudinally therethrough, the opening dimensioned to permit passage of the pair of jaw members in the closed position; and a movable handle movable relative to the housing, the movable handle operatively coupled to the pair of jaw members such that at least one of the jaw members is induced to move relative to the other jaw member between open and closed positions in response to movement of the movable handle with respect to the housing; and a lock movable between a first position wherein the lock engages the elongated shaft module to secure the elongated shaft module in place within the housing, and a second position wherein the lock is disengaged from the elongated shaft module to permit the elongated shaft module to be separated from the handle module.
 2. The surgical instrument according to claim 1, wherein the elongated shaft module includes a connector at a proximal end thereof for coupling the instrument to an external source of electrosurgical energy.
 3. The surgical instrument according to claim 2, wherein the elongated shaft module includes a contained electrical system therein, wherein the electrical system includes an electrical pathway extending between the connector and the end effector that is contained in a substantially moisture impervious casing.
 4. The surgical instrument according to claim 1, wherein the elongated shaft module includes a reciprocating drive rod extending at least partially through the elongated shaft member and operably coupled to the end effector and the movable handle to induce movement of the jaw members between the open and closed positions in response to movement of the movable handle with respect to the housing to reciprocate the drive rod.
 5. The surgical instrument according to claim 4, wherein the elongated shaft module includes a sealing member coupled to the elongated shaft member at a distal end thereof, the sealing member disposed between the elongated shaft member and the reciprocating drive rod to discourage contaminants from entering the elongated shaft member.
 6. The surgical instrument according to claim 5, wherein the sealing member is constructed of at least one of an o-ring, a wiper seal and a bellows.
 7. The surgical instrument according to claim 5, wherein the elongated shaft module includes a flexible seal member disposed between the jaw members and the outer shaft member, the flexible seal member constructed of heat-shrink tubing.
 8. The surgical instrument according to claim 4, wherein the jaw members are coupled to the reciprocating drive rod such that the jaw members are induced retract into elongated shaft member in response to reciprocation of the drive rod.
 9. A surgical instrument, comprising: a handle module including at least one handle providing gripping surfaces for holding the instrument by hand; and a drive assembly selectively removable from the handle assembly, the drive assembly including: an elongated shaft member defining a longitudinal axis; an end effector supported at a distal end of the elongated shaft member, the end effector including a pair of opposed jaw members wherein at least one of the jaw members is movable relative to the elongated shaft member between open and closed positions with respect to the other jaw member; a reciprocating drive member extending at least partially though the elongated shaft member, the drive member operably coupled to the end effector to induce movement of the jaw members between the open and closed positions in response to longitudinal reciprocation of the drive member; a motor operable to move the reciprocating drive member longitudinally through the elongated shaft; and a housing substantially surrounding the motor and the reciprocating drive member, the housing substantially impervious to moisture; and an actuator supported on the housing, the actuator operable to activate the motor.
 10. The surgical instrument according to claim 9, wherein the motor comprises a servomotor.
 11. The surgical instrument according to claim 9, wherein the motor comprises a linear motor including an electrical coil supported on the elongated shaft member and a magnet supported on the reciprocating drive member, the magnet longitudinally movable in response to a current in the electrical coil.
 12. The surgical instrument according to claim 9, wherein the drive assembly further includes a cable extending from the housing, the cable connectable to a source of electrosurgical energy.
 13. The surgical instrument according to claim 12, wherein the cable is in electrical communication with an electrical conduit extending through the elongated shaft member to transmit an electrosurgical current to the end effector.
 14. The surgical instrument according to claim 9, wherein the drive assembly includes at least one of a post and a slot disposed thereon configured to snap-fit to at least one of a post and a slot disposed on the handle assembly. 